There are lots of things that could have happened:
1. The update they pushed accidentally rolled back the previous update in power calculation. This wouldn't be the first time an update accidentally rolled back a previous bug fix.
2. They purposely altered the power calculation to prevent people from getting bugged node 12s in GW (people were using modded up tanks as their top 5 to artificially inflate their power level in order to make GW easier).
3. They updated the power calculation so it is more accurate. It was basically meaningless before anyway.
No one knows until a dev come see by and tells us what happened.
